1. Field of the Invention
This invention is concerned with the breaking or resolution of oil-in-water (O/W) bituminous emulsions by treatment with hydrophilic polyurethanes.
2. Description of the Prior Art
A great volume of hydrocarbons exist in known deposits of tar sands. These deposits occur at various places, the Athabasca tar sands in Canada being an example. The petroleum in a tar sand deposit is an asphaltic bitumen of a highly viscous nature ranging from a liquid to a semi solid. These bitumeninous hydrocarbons are usually characterized by being very viscous or even non flowable under reservoir conditions by the application of driving fluid pressure.
Where surface mining is not feasible, the bitumen must be recovered by rendering the tar material mobile in situ and producing it through a well penetrating the tar sand deposit. These in situ methods of recovery include thermal, both steam and in situ combustion and solvent techniques. Where steam or hot water methods are used, a problem results which aggravates the recovery of the bitumen. The difficulty encountered is emulsions produced by the in situ operations. These emulsions are highly stable O/W emulsions which are made even more stable by the usual presence of clays. Most liquid petroleum emulsions are water-in-oil (W/O) types. These normal W/O emulsions are broken by methods known in the art. However, the bitumen emulsions which are O/W types present a much different problem, and the same demulsifiers used in W/O emulsions will not resolve the O/W bitumen emulsions. The uniqueness of these O/W bitumen emulsions is described in C. W. W. Gewers, J. Canad. Petrol. Tech., 7(2), 89-90 (1968). (Prior art Reference A.) There is much prior art concerning the resolution of normal W/O emulsions. Some of the art even mistakenly equates bitumen O/W emulsions with these W/O emulsions. The following is a list of several art references.
B. British Pat. No. 1,213,392 discloses a polyurethane for breaking W/O emulsions.
C. British Pat. No. 1,112,908 discloses the compounds of the present invention, i.e. the hydrophilic polyurethanes. However, the British Patent is concerned only with W/O emulsions. Even in a discussion of prior art, this British Patent discusses hydrophilic polyurethanes and indicates that they are ineffective for breaking emulsions. This patent fails to teach one the specific criticality of using a hydrophilic polyurethane to break bitumen O/W emulsions as taught by the present specification.
D. U.S. Pat. No. 3,786,081 discloses the diol materials used in the present invention but is concerned only with breaking W/O emulsions.
E. U.S. Pat. No. 3,594,393 is also concerned with breaking W/O emulsions with polyurethanes.
F. U.S. Pat. No. 3,640,894 discloses polyurethanes and polyurethanes used in combination with Novolak alkoxylates to break W/O emulsions.
It is an object of the present invention to provide a method whereby O/W bitumen emulsions may be broken by treatment with a class of hydrophilic polyurethanes. Unlike the prior art, the present invention concerns a particular class of polyurethanes and recognizes the unique properties of bitumen O/W emulsions overlooked by the prior art.